Question

Account for the development of alkalinity in cultures capable of using ci- trate as their sole carbon source.

Answer 1

When citrate is used as the sole carbon source by organisms,then the citrate is acted upon by the enzyme citrase, which in turn produces oxaloacetic acid and acetate. These products are then with the help of enzymes are converted into pyruvic acid and carbon dioxide. During this reaction the meduim becomes alkaline i.e., the carbon dioxide that is generated combines with sodium and water to form sodium carbonate, and alkaline product. This is how the medium becomes alkaline.